Commit a6607930 authored Feb 03, 2014 by Tejun Heo Committed by Greg Kroah-Hartman Feb 07, 2014

kernfs: make kernfs_deactivate() honor KERNFS_LOCKDEP flag



kernfs_deactivate() forgot to check whether KERNFS_LOCKDEP is set
before performing lockdep annotations and ends up feeding
uninitialized lockdep_map to lockdep triggering warning like the
following on USB stick hotunplug.

 usb 1-2: USB disconnect, device number 2
 INFO: trying to register non-static key.
 the code is fine but needs lockdep annotation.
 turning off the locking correctness validator.
 CPU: 1 PID: 62 Comm: khubd Not tainted 3.13.0-work+ #82
 Hardware name: empty empty/S3992, BIOS 080011  10/26/2007
  ffff880065ca7f60 ffff88013a4ffa08 ffffffff81cfb6bd 0000000000000002
  ffff88013a4ffac8 ffffffff810f8530 ffff88013a4fc710 0000000000000002
  ffff880100000000 ffffffff82a3db50 0000000000000001 ffff88013a4fc710
 Call Trace:
  [<ffffffff81cfb6bd>] dump_stack+0x4e/0x7a
  [<ffffffff810f8530>] __lock_acquire+0x1910/0x1e70
  [<ffffffff810f931a>] lock_acquire+0x9a/0x1d0
  [<ffffffff8127c75e>] kernfs_deactivate+0xee/0x130
  [<ffffffff8127d4c8>] kernfs_addrm_finish+0x38/0x60
  [<ffffffff8127d701>] kernfs_remove_by_name_ns+0x51/0xa0
  [<ffffffff8127b4f1>] remove_files.isra.1+0x41/0x80
  [<ffffffff8127b7e7>] sysfs_remove_group+0x47/0xa0
  [<ffffffff8127b873>] sysfs_remove_groups+0x33/0x50
  [<ffffffff8177d66d>] device_remove_attrs+0x4d/0x80
  [<ffffffff8177e25e>] device_del+0x12e/0x1d0
  [<ffffffff819722c2>] usb_disconnect+0x122/0x1a0
  [<ffffffff819749b5>] hub_thread+0x3c5/0x1290
  [<ffffffff810c6a6d>] kthread+0xed/0x110
  [<ffffffff81d0a56c>] ret_from_fork+0x7c/0xb0

Fix it by making kernfs_deactivate() perform lockdep annotations only
if KERNFS_LOCKDEP is set.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Fabio Estevam <festevam@gmail.com>
Reported-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent fee0c54e

fs/kernfs/dir.c

+8 −4

Original line number	Diff line number	Diff line
		@@ -187,6 +187,7 @@ static void kernfs_deactivate(struct kernfs_node *kn)

		kn->u.completion = (void *)&wait;

		if (kn->flags & KERNFS_LOCKDEP)
		rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
		/* atomic_add_return() is a mb(), put_active() will always see
		* the updated kn->u.completion.
		@@ -194,13 +195,16 @@ static void kernfs_deactivate(struct kernfs_node *kn)
		v = atomic_add_return(KN_DEACTIVATED_BIAS, &kn->active);

		if (v != KN_DEACTIVATED_BIAS) {
		if (kn->flags & KERNFS_LOCKDEP)
		lock_contended(&kn->dep_map, _RET_IP_);
		wait_for_completion(&wait);
		}

		if (kn->flags & KERNFS_LOCKDEP) {
		lock_acquired(&kn->dep_map, _RET_IP_);
		rwsem_release(&kn->dep_map, 1, _RET_IP_);
		}
		}

		/**
		* kernfs_get - get a reference count on a kernfs_node

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